System and method for establishing communication with an array of inverters

ABSTRACT

A system and method for establishing communication between a controller and a plurality of inverters comprises determining a response time window length and broadcasting a response request to the array of inverters that includes the response time window length. Each inverter, in response to receiving the response requests, transmits a response to the controller at a randomly determined response time within the response time window. In response to receiving an acknowledgement from the controller, the responding inverter may ignore subsequent response requests. The controller may adjust the response time window and broadcasts the new response time window until no inverter response is received for a pre-determined number of response time windows.

CROSS-REFERENCE TO RELATED U.S. PATENT APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 12/902,046, entitled “System and Method for EstablishingCommunication with an Array of Inverters,” which was filed on Oct. 11,2010, the entirety of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates, generally, to power converters forconverting direct current (DC) power to alternating current (AC) powerand, more particularly, to systems and methods for controlling andcommunicating with such power converters.

BACKGROUND

Power inverters convert a DC power to an AC power. For example, somepower inverters are configured to convert the DC power to an AC powersuitable for supplying energy to an AC grid and, in some cases, an ACload coupled to the AC grid. One particular application for such powerinverters is the conversion of DC power generated by an alternativeenergy source, such as photovoltaic cells (“PV cells” or “solar cells”),fuel cells, DC wind turbine, DC water turbine, and other DC powersources, to a single-phase AC power for delivery to the AC grid at thegrid frequency.

In an effort to increase the amount of AC power generated, a largenumber of power inverters may be used in a particular application. Insome implementations, each power inverter is incorporated or otherwiseassociated with an alternative energy source to form an alternativeenergy source module. Such modules are typically located in remote orotherwise difficult to reach location (e.g., a solar cell panel locatedon a roof). As such, communicating with and/or controlling the invertersmay be accomplished remotely. However, in many implementations, theidentity and number of inverters used is unknown and/or may change overtime thereby increasing the difficulty of establishing and maintainingcommunication and control of the inverters.

SUMMARY

According to on aspect, a method for establishing communication with aplurality of inverters, which may be configured to convert directcurrent (DC) power generated from an alternative source to alternatingcurrent (AC) power, may include determining an initial length of aresponse time window. The method may also include broadcasting aresponse request to each inverter of the plurality of inverters thatprompts the inverter to respond. The response request may include thelength of the response time window. Additionally, the method mayinclude, in response to receiving a response from at least one inverterduring the response time window, (i) recording an identification of theat least one inverter and (ii) transmitting an acknowledgement to the atleast one inverter using the identification. Further, the method mayinclude, in response to the response time window expiring, (i) adjustingthe length of the response time window and (ii) broadcasting anotherresponse request that includes the adjusted length of the response timewindow to each inverter of the plurality of inverters.

In some embodiments, determining the initial length of the response timewindow may include determining the initial length based on apredetermined length of time required by an inverter of the plurality ofinverters to transmit a response to the response request. Additionally,in some embodiments, determining the initial length of the response timewindow may include determining an initial length of the response timewindow that is a multiple of the predetermined length of time requiredby the inverter to transmit the response to the response request.Additionally, broadcasting the response request may include broadcastingthe response request over an AC power line using a power linecommunication protocol.

Additionally, in some embodiments, receiving a response from the atleast one inverter may include receiving a response that includes anidentification number that uniquely identifies the responding inverterfrom the other inverters of the plurality of inverters and facilitatesdirected communication with the responding inverter using theidentification number. Further, transmitting the acknowledgement to theat least one inverter may include transmitting the acknowledgement afterexpiration of the time window. Additionally, in some embodiments,adjusting the length of the response time window may include decreasingthe length of the response time window by a multiple of a predeterminedlength of time required by an inverter of the plurality of inverters totransmit a response to the response request. Further, in someembodiments, adjusting the length of the response time window mayinclude increasing the length of the response time window in response toa number of communication collisions during the response time windowbeing greater than a predetermined value.

Additionally, the method may include incrementing a counter in responseto not receiving a response from at least one inverter of the pluralityof inverters during the response time window. In such embodiments,broadcasting another response request may include broadcasting anotherresponse request in response to the counter being less than a maximumthreshold value. Additionally, in some embodiments, the method mayfurther include stopping the broadcast of response requests in responseto the counter being equal to a maximum threshold value. Alternatively,in some embodiments, the method may include incrementing a counter inresponse to not receiving a response from at least one inverter of theplurality of inverters during the time window and repeating theadjusting step, the broadcasting another response step, and theincrementing step until the counter equals a predetermined thresholdvalue.

According to another aspect, a controller for communicating with aplurality of inverters over an alternating current (AC) power line mayinclude a communication circuit, a processor communicatively coupled tothe communication circuit, and a memory communicatively coupled to theprocessor. The inverters may be configured to convert direct current(DC) power from an alternative energy source to AC power. Thecommunication circuit may be configured to communicate with theplurality of inverters over the AC power line using a power linecommunication protocol. The memory may have stored therein a pluralityof instructions, which when executed by the processor, result in theprocessor determining an initial length of a response time window.Additionally, the plurality of instructions may result in the processorbroadcasting, using the communication circuit, a response request toeach inverter of the plurality of inverters that prompts the inverter torespond, the response request including the length of the response timewindow. Further, in response to receiving a response from at least oneinverter during the response time window, the plurality of instructionsmay result in the processor (i) storing an identification of the atleast one inverter in the memory and (ii) transmitting anacknowledgement, using the communication circuit, to the at least oneinverter using the identification. Yet further, in response to theresponse time window expiring, the plurality of instructions may resultin the processor (i) adjusting the length of the response time windowand (ii) broadcasting another response request, using the communicationcircuit, that includes the adjusted length of the response time windowto each inverter of the plurality of inverters.

In some embodiments, determining the initial length of the response timewindow may include determining the initial length based on apredetermined length of time required by an inverter of the plurality ofinverters to transmit a response to the response request. Additionally,in some embodiments, adjusting the length of the response time windowmay include decreasing the length of the response time window by amultiple of a predetermined length of time required by an inverter ofthe plurality of inverters to transmit a response to the responserequest. Further, in some embodiments, the plurality of instructions mayfurther result in the processor incrementing a counter in response tonot receiving a response from at least one inverter of the plurality ofinverters during the response time window. In such embodiments,broadcasting another response request may include broadcasting anotherresponse request in response to the counter being less than a maximumthreshold value.

In some embodiments, the plurality of instructions further may result inthe processor stopping the broadcast of response requests in response tothe counter being equal to a maximum threshold value. Additionally, insome embodiments, the plurality of instructions further result in theprocessor incrementing a counter in response to not receiving a responsefrom at least one inverter of the plurality of inverters during the timewindow and repeating the adjusting step, the broadcasting anotherresponse step, and the incrementing step until the counter equals apredetermined threshold value.

According to a further aspect, a method for establishing communicationbetween a controller and a plurality of inverters, which may beconfigured to convert direct current (DC) power from an alternativeenergy source to AC power, may include receiving with an inverter aresponse request transmitted by the controller, the response requestincluding a length of a response time window. Additionally, the methodmay include determining a random response time for the inverter based onthe length of the response time window and transmitting a response tothe controller at the response time. The response may include anidentification of the inverter. The method may also include, in responseto receiving an acknowledgement from the controller in response to thetransmitted response, ignoring subsequent response requests from thecontroller.

In some embodiments, receiving a response request may include receivinga response request that was broadcast from the controller over analternating current (AC) power line using a power line communicationprotocol. Additionally, determining a response time may includedetermining a response time that is within the response time window. Forexample, in some embodiments, determining a random response time mayinclude determining a random response time that is a multiple of thelength of time required by the inverter to transmit a response to theresponse request to the controller.

In some embodiments, ignoring subsequent response requests may includeignoring subsequent response requests from the controller for apredetermined amount of time. Additionally or alternatively, ignoringsubsequent response requests may include ignoring subsequent responserequests from the controller until a communication from the controlleris received that instructs the inverter to stop ignoring subsequentresponse requests. In some embodiments, the method may further include,in response to (i) not receiving an acknowledgement from the controllerin response to the transmitted response and (ii) receiving a subsequentresponse request from the controller that includes a length of asubsequent response time window, determining a subsequent response timefor the inverter based on the length of the subsequent response timewindow and transmitting a response to the controller at the responsetime, the response including the identification of the inverter.

According to yet another aspect, an inverter to convert direct current(DC) power from an alternative energy source to alternating current (AC)power may include a communication circuit, a processor communicativelycoupled to the communication circuit, and a memory devicecommunicatively coupled with the processor. The communication circuitmay be configured to communicate with a controller over an AC power lineusing a power line communication protocol. The memory device may includetherein a plurality of instructions, which when executed by theprocessor, result in the processor receiving a response requesttransmitted by the controller over the AC power line. The responserequest may include a length of a response time window. The plurality ofinstructions may also result in the processor determining a randomresponse time for the inverter based on the length of the response timewindow and transmitting a response to the controller at the responsetime. The response may include an identification of the inverter. Theplurality of instructions may further result in the processor, inresponse to receiving an acknowledgement from the controller in responseto the transmitted response, ignoring subsequent response requests fromthe controller.

In some embodiments, receiving a response request may include receivinga response request that was broadcast from the controller over analternating current (AC) power line using a power line communicationprotocol. Additionally, determining a random response time may includedetermining a random response time that is a multiple of the length oftime required by the inverter to transmit a response to the responserequest to the controller. Further, in some embodiments, ignoringsubsequent response requests may include ignoring subsequent responserequests from the controller for a predetermined amount of time.Additionally or alternatively, ignoring subsequent response requests mayinclude ignoring subsequent response requests from the controller untila communication from the controller is received that instructs theinverter to stop ignoring subsequent response requests. Further, in someembodiments, the plurality of instructions may also result in theprocessor, in response to (i) not receiving an acknowledgement from thecontroller in response to the transmitted response and (ii) receiving asubsequent response request from the controller that includes a lengthof a subsequent response time window, determining a subsequent responsetime for the inverter based on the length of the subsequent responsetime window and transmitting a response to the controller at theresponse time, the response including the identification of theinverter.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of one embodiment a system forgenerating alternative energy;

FIG. 2 is a simplified block diagram one embodiment of an alternativeenergy source module array and an alterative energy module arraycontroller of the system of FIG. 1;

FIG. 3 is a simplified flow diagram of one embodiment of a method forestablishing communications with an array of alternative energy modules;

FIG. 4 is a simplified flow diagram of one embodiment of a method fordiscovering the alternative energy modules of the alternative energymodule array of FIG. 2; and

FIG. 5 is a simplified flow diagram of one embodiment of a method forestablishing communication with the alternative energy module arraycontroller of FIG. 2

DETAILED DESCRIPTION

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

Some embodiments of the disclosure, or portions thereof, may beimplemented in hardware, firmware, software, or any combination thereof.Embodiments of the disclosure may also be implemented as instructionsstored on a tangible, machine-readable medium, which may be read andexecuted by one or more processors. A machine-readable medium mayinclude any mechanism for storing or transmitting information in a formreadable by a machine (e.g., a computing device). For example, amachine-readable medium may include read only memory (ROM); randomaccess memory (RAM); magnetic disk storage media; optical storage media;flash memory devices; and others.

Referring to FIG. 1, in one embodiment, a system 100 for generatingalternative energy includes an array 102 of alternative energy sourcemodules 104 and a module array controller 106 electrically coupled toeach alternative energy source module 104 via an alternating current(“AC”) power line(s) 108. The alternative energy source modules 104 areconfigured to convert direct current (“DC”) power from an alternativeenergy source to AC power, which may be supplied to a load (e.g., theutility grid) via the power line(s) 108. In the illustrative embodiment,the alternative energy source modules 104 are embodied as photovoltaicmodules configured to convert solar energy to AC power. However, inother embodiments, other types of alternative energy sources may be usedsuch as, for example, fuel cells, DC wind turbines, DC water turbines,and/or other alternative energy sources. Additionally, although theillustrative array 102 includes four alternative energy source modules104, the array 102 may include more or less modules 104 in otherembodiments.

The array 102 of alternative energy source modules 104 is locatedremotely from the module array controller 106. For example, in theillustrative embodiment, the array 102 is attached to a roof 110 of abuilding 112, such as a residential home, apartment, business, or otherstructure. Of course, in other embodiments, the array 102 may bepositioned in other locations depending on, for example, the type ofalternative energy used. Additionally, the alternative energy sourcemodules 104 may or may not be located near each other. For example, thearray 102 may be embodied as a plurality of sub-arrays, each locatedapart from each other and having a plurality of alternative energysource modules 104. Additionally, although a single AC power line 108 isillustrated as coupling the modules 104 to the controller 106 in FIG. 1,it should be appreciated that the AC power line 108 may be embodied as aplurality of AC power lines in other embodiments.

The system 100 may also include a communication gateway 114 and anetwork interface device 116 in some embodiments. In the illustrativeembodiment, the communication gateway 114 is embodied as a wirelesscommunication device configured to communicate with the module arraycontroller 106 via a wireless communication link 118. The controller 106and the wireless communication link 118 may use any suitable wirelesscommunication protocol to effect such communication. For example, in oneembodiment, the controller 106 is configured to communicate with thecommunication gateway 114 using a ZigBee communication protocol. Ofcourse, other wireless communication protocols may be used in otherembodiments. Additionally, in some embodiments, the controller 106 andthe communication gateway 114 may be configured to communicate using awired communication protocol over a wired communication link (i.e., thecommunication link 118 is a wired communication link in suchembodiments).

The communication gateway 114 is also configured to communicate with anetwork interface device 116 via a communication link 120. Thecommunication link 120 may be embodied as a wired or wirelesscommunication link, and the communication gateway 114 may be configuredto communicate with the network interface device 116 using a wired orwireless communication protocol. For example, in the illustrativeembodiment, the communication gateway 114 is configured to communicatewith the network interface device 116 using a ZigBee communicationprotocol.

The network interface device 116 is illustratively embodied as a datarouter, but may be embodied as other networking or communication routingdevices in other embodiments. The network interface device 116 allowsvarious computing devices to communicate with or otherwise receive datafrom the module array controller 106. For example, in some embodiments,the system 100 may include a computer 122 communicatively coupled to thenetwork interface device 116. In such embodiments, a user (e.g., ahomeowner) may use the computer 122 to interact with and/or receive datafrom the module array controller 106. The computer 122 may be embodiedas any type of computing device such as a desktop computer, a laptopcomputer, a mobile computing device, a “smart” phone, or other devicecapable of communicating with the network interface device 116.

In some embodiments, the network interface device 116 is alsocommunicatively coupled to a network 124 via a communication link 126,which may be embodied as a wired and/or wireless communication link. Thenetwork 124 may be embodied as any number of various wired and/orwireless networks. For example, the network 124 may be embodied as orotherwise include one or more local area networks, wide area networkspublicly available global networks (e.g., the Internet), or anycombination thereof. Furthermore, the network 124 may include any numberof additional devices to facilitate remote communication with thenetwork interface device 116 and may support any wired and/or wirelesscommunication protocol.

In some embodiments, the system 100 may further include remote computingdevices configured to remotely communicate with the module arraycontroller 106 and/or other devices of the system 100. For example, theillustrative system 100 includes a data management server 128, which maybe configured to receive data from the module array controller 106 viathe network 124. Such data may include, for example, power generationdata, service/maintenance data, error data, and/or any other datarelated to the alternative energy source modules 104. The datamanagement server 128 may be embodied as any type of computer server andmay include any number of computers, databases, networking equipment,and/or other computing devices.

The system 100 may also include other remote computers 130, which mayoperate as clients and/or servers in the system 100. For example, theremote computers 130 may be operated by alternative energy source moduleinstallation companies to control, monitor, and/or communicate with themodule array controller 106. In this way, the installation company canmonitor the performance and “health” of the alternative energy sourcemodules 104 and controller 106. Additionally, such computers 130 maycommunicate with the data management server 128 to request additionaldata related to the system 100.

Referring now to FIG. 2, as discussed above, the illustrativealternative energy source modules 104 are embodied as photovoltaicmodules configured to convert solar energy to AC power. Each of themodules 104 includes a DC photovoltaic module 200 and an inverter 202.The DC photovoltaic module 200 may be embodied as one or morephotovoltaic cells and is configured to deliver DC power to the inverter202 in response to receiving an amount of sunlight. Of course, the DCpower delivered by DC photovoltaic module 200 is a function ofenvironmental variables, such as, e.g., sunlight intensity, sunlightangle of incidence and temperature. The inverter 202 is configured toconvert the DC power generated by the DC photovoltaic module 200 to ACpower. In some embodiments, the inverter 202 and the DC photovoltaicmodule 200 are located in a common housing. Alternatively, the inverter202 may include its own housing secured to the housing of the DCphotovoltaic module 200. Additionally, in some embodiments, the inverter202 is separate from the housing of the DC photovoltaic module 200, butlocated nearby.

The illustrative inverter 202 includes a DC-to-AC inverter 204 and aninverter controller 206. The DC-to-AC inverter 204 is configured toconvert the DC power generated by the DC photovoltaic module 200 to ACpower at the grid frequency. One of a number of various invertertopologies and devices may be used in the DC-to-AC inverter 204.Examples of inverter topologies that may be used in the inverter 204 aredescribed in, for example, U.S. patent application Ser. No. 12/563,499,entitled “Apparatus for Converting Direct Current to AlternatingCurrent” by Patrick L. Chapman et al., filed on Sep. 21, 2009 and inU.S. patent application Ser. No. 12/563,495, entitled “Apparatus andMethod for Controlling DC-AC Power Conversion” by Patrick L. Chapman etal., filed on Sep. 21, 2009.

The operation of the inverter 204 is controlled and monitored by theinverter controller 206. The illustrative inverter controller 206includes a processor 210, a memory 212, and a communication circuit 214.Additionally, the inverter controller 206 may include other devicescommonly found in controllers, which are not illustrated in FIG. 2 forclarity of description. Such additional devices may include, forexample, peripheral devices, data storage devices, input/output ports,and/or other devices.

The processor 210 of the inverter controller 206 may be embodied as anytype of processor capable of executing software/firmware, such as amicroprocessor, digital signal processor, microcontroller, or the like.The processor 210 is illustratively embodied as a single core processor,but may be embodied as a multi-core processor having multiple processorcores in other embodiments. Additionally, the inverter controller 206may include additional processors 210 having one or more processor coresin other embodiments.

The memory 212 of the inverter controller 206 may be embodied as one ormore memory devices or data storage locations including, for example,dynamic random access memory devices (DRAM), synchronous dynamic randomaccess memory devices (SDRAM), double-data rate synchronous dynamicrandom access memory device (DDR SDRAM), flash memory devices, and/orother volatile memory devices. The memory 212 is communicatively coupledto the processor 210 via a number of signal paths, such as a data bus.Although only a single memory device 212 is illustrated in FIG. 2, inother embodiments, the inverter controller 206 may include additionalmemory devices. Various data and software may be stored in the memorydevice 212. For example, applications, programs, libraries, and driversthat make up the firmware executed by the processor 210 may reside inmemory 212.

The communication circuit 214 may be embodied as any number of devicesand circuitry for enabling communications between the inverter 202 andthe controller 106. In the illustrative embodiment, the communicationcircuit 214 is configured to communicate with the controller 106 overthe AC power line(s) 108 and may use any suitable power linecommunication protocol to effect such communication. For example, insome embodiments, the communication circuit 214 may use the CENELEC Bband power line communication protocol but may use other protocols inother embodiments such as those protocols including a form of errordetection and/or correction. Alternatively, in other embodiments, thecommunication circuit 214 may be configured to communicate with thecontroller 106 using a wired or wireless communication protocol. In suchembodiments, the system 100 includes a suitable communication link(e.g., a dedicated communication cable) between each inverter 202 andthe controller 106.

As discussed above, the module array controller 106 is configured tomonitor and/or control the operation of the alternative energy sourcemodules 104. The illustrative module array controller 106 includes aprocessor 220, a memory 222, and a communication circuit 224.Additionally, the module array controller 106 may include other devicescommonly found in controllers, which are not illustrated in FIG. 2 forclarity of description. Such additional devices may include, forexample, peripheral devices, data storage devices, input/output ports,and/or other devices.

The processor 220 of the module array controller 106 may be embodied asany type of processor capable of executing software/firmware, such as amicroprocessor, digital signal processor, microcontroller, or the like.The processor 220 is illustratively embodied as a single core processor,but may be embodied as a multi-core processor having multiple processorcores in other embodiments. Additionally, the module array controller106 may include additional processors 220 having one or more processorcores in other embodiments.

The memory 222 of the module array controller 206 may be embodied as oneor more memory devices or data storage locations including, for example,dynamic random access memory devices (DRAM), synchronous dynamic randomaccess memory devices (SDRAM), double-data rate synchronous dynamicrandom access memory device (DDR SDRAM), flash memory devices, and/orother volatile memory devices. The memory 222 is communicatively coupledto the processor 220 via a number of signal paths, such as a data bus.Although only a single memory device 222 is illustrated in FIG. 2, inother embodiments, the module array controller 106 may includeadditional memory devices. Various data and software may be stored inthe memory device 222. For example, applications, programs, libraries,and drivers that make up the software/firmware executed by the processor220 may reside in memory 222.

Similar to the communication circuit 214, the communication circuit 224may be embodied as any number of devices and circuitry for enablingcommunications between the controller 106 and the inverter 202. In theillustrative embodiment, the communication circuit 224 is configured tocommunicate with the inverter 202 over the AC power line(s) 108 and mayuse any suitable power line communication protocol to effect suchcommunication. For example, in some embodiments, the communicationcircuit 224 may use the CENELEC B power line communication protocol butmay be use other protocols in other embodiments such as those protocolsincluding a form of error detection and/or correction. Alternatively, asdiscussed above, the communication circuit 224 may be configured tocommunicate with the inverter 202 using a wired or wirelesscommunication protocol.

In some embodiments, the module array controller 106 may also include awireless communication circuit 226. In such embodiments, the wirelesscommunication circuit 226 may be embodied as any number of devices andcircuitry to facilitate communication between the controller 106 and thenetwork interface device 116 over the communication link 120. To do so,the communication circuit 226 may use any suitable wirelesscommunication protocol, such as a ZigBee communication protocol. Ofcourse, as discussed above in regard to FIG. 1, the communicationcircuit 226 may be configured to communicate with the network interfacedevice 116 using a wired communication protocol and hardware. In suchembodiments, the communication link 120 is embodied as or otherwiseincludes a wired communication link.

As discussed above, in use, the module array controller 106 isconfigured to establish communications with each of the inverters 202 ofthe array 102 of alternative energy source modules 104. However, thecontroller 106 may not know the number of inverters 202 (i.e., thenumber of modules 104) or the identification (e.g., the media accesscontrol (MAC) address or other number/data required to directlycommunicate with each inverter 202) of each inverter 202 of the array102. As such, the controller 106 may execute a method 300 forestablishing communications with the inverters 202 as illustrated inFIG. 3. The method 300 begins with block 302 in which the controller 106performs various initialization procedures. Such initializationprocedures may include initialization of registers and devices, loadingof firmware and software, and/or other procedures required to configurethe controller 106 for communicating with the inverters 202.

In block 304, the controller 106 performs a discovery process toidentify each inverter 202 of the array 102 and obtain the informationnecessary to directly communicate with each inverter 202. After thediscovery process is completed, the controller 106 communicates and/orcontrols the operation of the modules 104 (i.e., inverters 202) in block306 as needed. It should be appreciated that during use, modules 104 maybe added or removed from the array 102. For example, if a module 104, ora component of the module 104, becomes defective, the module 104 orcomponent thereof (e.g., inverter 202) may be replaced. Additionally,based on the change of power requirements, modules 104 may be added orremoved from the array 102 over time. As such, the controller 106determines if the module array has been modified in block 308. If so,the method 300 loops back to block 304 wherein the controller 106performs the discovery process again to determine the identity of eachmodule 104 (i.e., inverter 202). If not, the method 300 loops back toblock 306 wherein the controller 106 continues to communicate with themodules 104 as needed. The controller 106 may determine that the array102 has been modified based on a direct input supplied to the controller106 (e.g., an installer informing the controller 106 that a module 104has been added), based on a failure to communicate with one or moremodules 104, or based on some other criteria.

Referring now to FIG. 4, one embodiment of a method 400 for discoveringeach inverter 202 of the array 102, which may be used by the controller106 in the discovery process of block 304 of method 300, is shown. Themethod 400 begins with block 402 in which the controller 106 determinesan initial response time window length. The response time windowrepresents a length of time during which the inverters 202 of themodules 104 may respond to a response request transmitted by thecontroller 106 as discussed in more detail below. The controller 106 mayuse any suitable algorithm to determine the initial length of theresponse time window. In one particular embodiment, the controller 106is configured to determine the length of the response time window basedon the length of time required for an inverter 202 to transmit theresponse to the controller 106 multiplied by the expected maximum numberof modules 104 in the array 102. For example, if the inverter 202requires 500 milliseconds to transmit the response to the controller 106and the expected maximum number of modules 104 in the array 102 isdetermined to be 200, the controller 106 may set the initial length ofthe response time window to about 100 seconds (i.e., 500milliseconds*200 modules). The length of time required by the inverter202 to transmit the response to the controller 106 may be based on orotherwise affected by the communication protocol used, the communicationcircuitry used, the data size of the response, and/or other parameters.The expected maximum number of modules 104 in the array 102 may be anarbitrary maximum number or based on an estimated maximum size of thearray 102 (e.g., based on a maximum physical and/or electricalcapacity). Alternatively, in other embodiments, the controller 106 maybe configured to simply use an arbitrary, large length of time for theinitial response time window.

In block 404, the controller 106 broadcasts a response request, which isreceived by each of the inverters 202. The response request includes thelength of the response time window determined in block 406. The responserequest prompts each of the inverters 202 to respond to the request bytransmitting identification data related to the respective inverter 202to the controller 106. In block 406, the controller 106 determineswhether a response has been received from one of the inverters 202 inresponse to the response request. If so, the controller 208 records theidentification data received in the response from the inverter 202. Forexample, the controller 208 may store the identification data in thememory 222 or other storage device. As discussed in more detail below,the identification data uniquely identifies the inverter 202 from theother inverters of the array 102 and allows the controller 208 todirectly communicate with the responding inverter 202 (e.g., theidentification data may include a MAC address associated with theresponding inverter 202).

In block 410, the controller 106 determines whether the response timewindow has expired. If not, the method 400 loops back to block 406wherein the controller 106 again monitors for responses from theinverters 202. However, if the controller 106 determines that theresponse time window has expired in block 410, the controller 106determines if at least one response was received from an inverter 202 inthe last response time window in block 412. If so, the controller 106transmits an acknowledgment to each of the responding inverters 202 inblock 414. The acknowledgment may be embodied as any type ofcommunication capable of informing the responding inverters 202 that thecontroller 106 has received their respective responses. As discussed inmore detail below in regard to FIG. 5, the acknowledgement may alsoprompt the responding inverters 202 to ignore subsequent responserequests from the controller 106.

Subsequently, in block 416, the controller 106 adjusts the length of theresponse time window. In some embodiments, the controller 106 isconfigured to decrease the length of the response time window in block416. For example, the controller 106 may be configured to decrease thelength of the response time window by a predetermined multiple of thelength of time required by an inverter 202 to transmit a response to theresponse request. For example, in the example described above, thecontroller 106 may be configured to decrease the response time window bya multiple of 500 milliseconds (e.g., 500 ms, 1000 ms, 1500 ms, etc.),which was the length of time required for an inverter 202 to respond. Insome embodiments, a minimum response time window length may be used ifthe adjusted would reduce the length of the response time window below aminimum length.

In other embodiments, the controller 106 may decrease the responsewindow time by an arbitrary, predetermined amount. Additionally, in someembodiments, the adjustment made to the response time window in block416 may be based on other criteria. For example, the adjustment may bebased on the number of data collisions detected by the controller 106 inthe previous response time window or on the expected remaining number ofnon-responding inverters 202. In such embodiments, the length of theresponse time window may be decreased, may be increased, or may remainthe same.

In block 418, the controller 106 resets a time-out counter. As discussedbelow in more detail, the time-out counter is used to estimate when allof the inverters 202 of the array 102 have been discovered and respondedto the controller 106. As such, if at least one response was received inthe current response time window, the controller 106 resets the time-outcounter in block 418. After the time-out counter is reset in block 418,the method 400 loops back to block 404 in which the controller 106broadcasts another response request, which includes the adjustedresponse time window length.

Referring back to block 412, if the controller 106 determines that noresponse was received from any inverters 202 in the current responsetime window, the method 400 advances to block 420. In block 420, thecontroller 106 increments the time-out counter. As discussed above, thetime-out counter is used to estimate when all of the inverters 202 ofthe array 102 have been discovered. As such, in block 422, thecontroller 106 determines if the time-out counter is equal to apredetermined threshold value. If not, the method 400 advances to block416 in which the response time window length is adjusted. However, ifthe time-out counter is determined to be equal to the predeterminedthreshold value in block 422, the controller 106 determines that all ofthe inverters 202 of the array 102 have been discovered and ends thediscovery process in block 424. In one particular embodiment, thepredetermined threshold value is set to three. As such, the controller106 will continue to broadcast response requests until no response isreceived from an inverter 202 in three consecutive response timewindows. Of course, other values for the predetermined threshold valuemay be used in other embodiments.

Referring now to FIG. 5, each of the inverters 202 of the modules 104 ofthe array 102 may execute a method 500 for establishing communicationwith the alternative energy module array controller 106. The method 500begins with block 502 in which the inverter 202 performs variousinitialization procedures. Such initialization procedures may includeinitialization of registers and devices, loading of firmware andsoftware, and/or other procedures required to configure the inverter 202for communicating with the controller 106. Subsequently, in block 504,the inverter 202 determines whether a response request was received fromthe controller 106. As discussed above in regard to FIG. 4, the responserequest is broadcast by the controller 106 and, as such, received byeach inverter 202. If no response request has been received, the method500 loops back to block 504 in which the inverter 202 continues tomonitor for a broadcast from the controller 106.

If, however, the inverter 202 receives a response request from thecontroller 106 in block 504, the inverter 202 determines a response timeto respond to the response request in block 506. The response time isbased on the length of the response time window, which is included inthe response request received from the controller 106. In theillustrative embodiment, the inverter 202 is configured to randomlydetermine a response time within the response time window at which tosend its response to the controller 106. Such response times may bemultiples of the length of time required by the inverter 202 to send theresponse to the controller 106. For example, returning to the previousexample, the response time determine by the inverter 202 in block 506may be a random integer multiple of 500 ms, which was the estimated timeto transmit the response to the controller 106. In this way, each of theinverters 202 randomly selects a timeslot of the response time window inwhich to send its response to the controller 106. As such, the responsesfrom the inverters 202 are spread across the response time window,thereby reducing the likelihood of communication collisions.

In block 508, the inverter 202 transmits a response to the controller106 at the response time determined in block 506. As discussed above,the response includes identification data that uniquely identifies theresponding inverter 202 from the other inverters 202 of the array 102.Additionally, the identification data may be used by the controller 106to send direct communications (e.g., a unicast) to the respondinginverter 202. For example, the identification data may include the MACaddress of the responding inverter 202.

After the inverter 202 has transmitted its response in block 508, theinverter 202 determines if an acknowledgment has been received from thecontroller 106 in block 510. If no acknowledgement has been received,the inverter 202 determines if a wait period has expired in block 512.If not, the inverter 202 continues to monitor for an acknowledgementfrom the controller 106 in blocks 510, 512 until an acknowledgment isreceived or the wait period expires. The wait period may be an arbitrarywait period, based on the response window time, or some other criteria.After the wait period expires (or other wait period lapses) with noacknowledgment received, the method 500 loops back to block 504 in whichthe inverter continues to monitor for response requests from thecontroller 106.

Referring back to block 510, if an acknowledgement is received from thecontroller 106, the method 500 advances to block 514. In block 514, theinverter 202 ignores any subsequent response requests received from thecontroller 106. In this way, the amount of response traffic is reducedover time as the number of acknowledged inverters increases.

In some embodiments, the discovery process may be restarted at a latertime. As such, the inverter 202 determines if the discovery process hasbeen reinitiated in block 516. If not, the method 500 loops back toblock 514 wherein the controller continues to ignore response requestsfrom the controller 106. However, if the discovery process has beenreinitiated in block 516, the method 500 loops back to block 504 inwhich the inverter continues to monitor for response requests from thecontroller 106. As discussed above, the discovery process may bereinitiated after a predetermined lapse of time, in response to thearray 102 being modified, or based on some other criteria.

There is a plurality of advantages of the present disclosure arisingfrom the various features of the apparatuses, circuits, and methodsdescribed herein. It will be noted that alternative embodiments of theapparatuses, circuits, and methods of the present disclosure may notinclude all of the features described yet still benefit from at leastsome of the advantages of such features. Those of ordinary skill in theart may readily devise their own implementations of the apparatuses,circuits, and methods that incorporate one or more of the features ofthe present disclosure and fall within the spirit and scope of thepresent invention as defined by the appended claims.

1. A method for establishing communication between a controller and aplurality of inverters, the inverters configured to convert directcurrent (DC) power from an alternative energy source to AC power, themethod comprising: receiving with an inverter a response requesttransmitted by the controller, the response request including a lengthof a response time window; determining a random response time for theinverter based on the length of the response time window; transmitting aresponse to the controller at the response time, the response includingan identification of the inverter; and in response to receiving anacknowledgement from the controller in response to the transmittedresponse, ignoring subsequent response requests from the controller. 2.The method of claim 1, wherein receiving a response request comprisesreceiving a response request that was broadcast from the controller overan alternating current (AC) power line using a power line communicationprotocol.
 3. The method of claim 1, wherein determining a response timecomprises determining a response time that is within the response timewindow.
 4. The method of claim 3, wherein determining a random responsetime comprises determining a random response time that is a multiple ofthe length of time required by the inverter to transmit a response tothe response request to the controller.
 5. The method of claim 1,wherein ignoring subsequent response requests comprises ignoringsubsequent response requests from the controller for a predeterminedamount of time.
 6. The method of claim 1, wherein ignoring subsequentresponse requests comprises ignoring subsequent response requests fromthe controller until a communication from the controller is receivedthat instructs the inverter to stop ignoring subsequent responserequests.
 7. The method of claim 1, further comprising: in response to(i) not receiving an acknowledgement from the controller in response tothe transmitted response and (ii) receiving a subsequent responserequest from the controller that includes a length of a subsequentresponse time window: determining a subsequent response time for theinverter based on the length of the subsequent response time window; andtransmitting a response to the controller at the response time, theresponse including the identification of the inverter.
 8. An inverter toconvert direct current (DC) power from an alternative energy source toalternating current (AC) power, the inverter comprising: a communicationcircuit to communicate with a controller over an AC power line using apower line communication protocol; a processor communicatively coupledto the communication circuit; and a memory device communicativelycoupled with the processor and having stored therein a plurality ofinstructions, which when executed by the processor, result in theprocessor: receiving a response request transmitted by the controllerover the AC power line, the response request including a length of aresponse time window; determining a random response time for theinverter based on the length of the response time window; transmitting aresponse to the controller at the response time, the response includingan identification of the inverter; and in response to receiving anacknowledgement from the controller in response to the transmittedresponse, ignoring subsequent response requests from the controller. 9.The inverter of claim 8, wherein receiving a response request comprisesreceiving a response request that was broadcast from the controller overan alternating current (AC) power line using a power line communicationprotocol.
 10. The method of claim 8, wherein determining a randomresponse time comprises determining a random response time that is amultiple of the length of time required by the inverter to transmit aresponse to the response request to the controller.
 11. The inverter ofclaim 8, wherein ignoring subsequent response requests comprisesignoring subsequent response requests from the controller for apredetermined amount of time.
 12. The inverter of claim 8, whereinignoring subsequent response requests comprises ignoring subsequentresponse requests from the controller until a communication from thecontroller is received that instructs the inverter to stop ignoringsubsequent response requests.
 13. The inverter of claim 8, wherein theplurality of instructions further cause the inverter to: in response to(i) not receiving an acknowledgement from the controller in response tothe transmitted response and (ii) receiving a subsequent responserequest from the controller that includes a length of a subsequentresponse time window: determining a subsequent response time for theinverter based on the length of the subsequent response time window; andtransmitting a response to the controller at the response time, theresponse including the identification of the inverter.